A typical example of cured resins put into practical application as an optical lens is a poly[-diethylene glycol bis(ally carbonate)]. This resin, having high impact resistance, lightweightness and excellent dyeability, is in wide use as a spectacle lens for eyesight correction. The poly[diethylene glycol bis(ally carbonate)], however, has a drawback of low refractive index (1.50) and has no sufficient property. Spectacle lenses are required to have a small thickness at the periphery and lightweightness. A lens has a smaller thickness at the periphery when the lens has a higher refractive index, and a smaller lens thickness results in a lighter lens weight. A lighter lens weight is also obtained when the lens material, i.e. the material composition for lens has a smaller specific gravity. Hence, a lens having a refractive index sufficiently higher than that of the poly[diethylene glycol bis(allyl carbonate)]is desired.
A number of resins were proposed each as a resin for high refractive index lens. They are, for example, a resin obtained by a reaction between a bromine atom-containing hydroxy compound and an isocyanate compound (Japanese Laid-Open Patent Application No. 164615/1983), a resin obtained by a reaction between a sulfur atom-containing polyol compound and a polyisocyanate compound (Japanese Laid-Open Patent Application No. 217229/1985), a resin obtained by a reaction between a polythiol compound and a polyisocyanate compound (Japanese Laid-Open Patent Application No. 199016/1985), and a resin comprising a bromine atom-containing aromatic acrylic compound (Japanese Laid-Open Patent Application No. 104901/1982).
However, the resin comprising a bromine atom-containing aromatic acrylic compound has a high specific gravity and the resins obtained by a reaction between a polyol compound or a polythiol compound and a polyisocyanate compound have low heat resistance.
The present inventors previously found a resin obtained from a sulfur-containing aromatic vinyl compound and an isocyanate compound, as a resin for lens of high refractive index, small specific gravity, high strengths and high heat resistance (Japanese Laid-Open Patent Application No. 197514/1989). The present inventors made further study on a resin capable of giving a lens of higher refractive index, small specific gravity, high strengths and high heat resistance and completed the present invention.